Every week, many of the operators
reading this article spend their morning driving from sample station to sample
station, very carefully filling little 100 mL bottles with water from their
distribution system. Once per quarter or
per month, they probably do the same thing for the water from each and every
operating well. And if they work at a
surface water treatment plant, they take a great many more of those samples. They cap the bottles, label them
appropriately, and prepare them for transport to the laboratory where they will
be tested for Total Coliform (TC) Bacteria.
If the test is positive, then the sample will also be tested for a specific
TC bacteria, Escherichia coli, more
commonly known as E. coli. So what is a coliform bacterium and why do we
test for it? Coliform bacteria are
defined as rod-shaped Gram-negative non-spore forming bacteria which can
ferment lactose with the production of acid and gas when incubated at 35-37°C1. That’s a mouthful! In other words, a coliform bacteria is one
that gives a positive test result; not a real meaningful definition. In theory, the coliform test is used to try
and detect bacteria that may be present because of contamination by animal
feces, sewage, or sewage contaminated water.
A great many of the bacteria that live in the gut of mammals like humans
are coliform bacteria. However, coliform
bacteria can and do live just about anywhere: in the soil; in surface and
groundwater; in and on plants, flowers and fruits; everywhere! So just because there may be a positive
coliform sample doesn’t mean that the water is contaminated. It is just an indicator that there could
possibly be a problem, and that you should do some investigating to see if
there are any problems you weren’t aware of in your system: maybe a leak, an
unprotected backflow situation, low chlorine residuals, etc. We are required to test for these bacteria
in the distribution system by the Total Coliform Rule (
·
Maintains the routine sampling structure of the
original TCR
·
Reduces the required number of follow-up samples
(repeat and additional routine) for systems serving ≤1,000
·
Like TCR ,
reduced monitoring is available for small systems
·
Provides more stringent criteria that systems
must meet to qualify for and stay on reduced monitoring
·
Requires small systems with problems to monitor
more frequently
·
RTCR requires Public Water Systems to
investigate the system and correct any sanitary defects found when monitoring
results show the system may be vulnerable to contamination
·
Systems must conduct a basic self assessment
(Level 1) or a more detailed assessment by a qualified party (Level 2) depending
on the severity and frequency of contamination
·
Failure to assess and correct is a Treatment
Technique (TT) violation
·
Notify public within 24 hours if system confirms
fecal contamination (E. coli)
·
Total Coliform MCL
/ acute violation is eliminated
·
Notify public within 30 days if system does not
investigate and fix any identified problems
·
Notify public yearly regarding monitoring,
reporting and recordkeeping violations
The Revised Total Coliform Rule
is a good thing, no doubt about it. It
removes stringent regulations regarding total coliform bacteria, which turned
out to be not as good an indicator of fecal contamination as it was once thought. Instead, it relies more heavily on the
investigation and correction of distribution system issues that could
potentially be a source of contamination into the system. And maintaining the treatment and distribution
systems are, of course, what those same operators who go out and collect all these
samples do on an every day basis anyway.
For more information on the
Revised Total Coliform Rule, go to EPAs website at
1. American
Public Health Association, Standard Methods for the Examination of Water and
Wastewater, 19th ed., APHA, Washington , DC
